Because the tube is swollen shut, the pressure cannot equalize. The resulting vacuum or fluid buildup pulls on your eardrum, causing that muffled sensation and sometimes pain.

Never combine a decongestant with the Valsalva maneuver. Decongestants can cause a temporary pressure spike. Wait 1 hour after taking one before trying to pop your ears.

Once the inflammation is managed, you can try to manually open the tubes. Think of these as gentle ways to "inflate" the tube from the inside.

These methods focus on manually opening the Eustachian tubes to equalize pressure: Blocked ears from cold: what to do - Boots Hearingcare